Fixed memory allocation problems when compressing multi-MB
items. Lookup history is now a double linked list, used in a wrap-around style. Jan
This commit is contained in:
Jan Wieck
parent
6a00a7eb72
commit
9b0fe4eee2
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@ -1,7 +1,7 @@
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/* ----------
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* pg_lzcompress.c -
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*
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.7 2000/07/06 21:02:07 wieck Exp $
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/pg_lzcompress.c,v 1.8 2000/07/20 14:23:28 wieck Exp $
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*
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* This is an implementation of LZ compression for PostgreSQL.
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* It uses a simple history table and generates 2-3 byte tags
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@ -185,9 +185,9 @@
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* Local definitions
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* ----------
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*/
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#define PGLZ_HISTORY_SIZE 8192
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#define PGLZ_HISTORY_LISTS 8192
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#define PGLZ_HISTORY_MASK 0x1fff
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#define PGLZ_HISTORY_PREALLOC 8192
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#define PGLZ_HISTORY_SIZE 4096
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#define PGLZ_MAX_MATCH 273
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@ -200,6 +200,7 @@
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typedef struct PGLZ_HistEntry
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{
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struct PGLZ_HistEntry *next;
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struct PGLZ_HistEntry *prev;
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char *pos;
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} PGLZ_HistEntry;
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@ -209,7 +210,7 @@ typedef struct PGLZ_HistEntry
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* ----------
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*/
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static PGLZ_Strategy strategy_default_data = {
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256, /* Data chunks smaller 256 bytes are nott
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256, /* Data chunks smaller 256 bytes are not
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* compressed */
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6144, /* Data chunks greater equal 6K force
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* compression */
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@ -247,6 +248,12 @@ static PGLZ_Strategy strategy_never_data = {
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};
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PGLZ_Strategy *PGLZ_strategy_never = &strategy_never_data;
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/* ----------
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* Global arrays for history
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* ----------
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*/
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static PGLZ_HistEntry *hist_start[PGLZ_HISTORY_LISTS];
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static PGLZ_HistEntry hist_entries[PGLZ_HISTORY_SIZE];
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/* ----------
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@ -276,11 +283,26 @@ PGLZ_Strategy *PGLZ_strategy_never = &strategy_never_data;
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* Adds a new entry to the history table.
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* ----------
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*/
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#define pglz_hist_add(_hs,_hn,_s,_e) { \
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#define pglz_hist_add(_hs,_he,_hn,_s,_e) { \
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int __hindex = pglz_hist_idx((_s),(_e)); \
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(_hn)->next = (_hs)[__hindex]; \
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(_hn)->pos = (_s); \
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(_hs)[__hindex] = (_hn)++; \
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if ((_he)[(_hn)].prev == NULL) { \
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(_hs)[__hindex] = (_he)[(_hn)].next; \
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} else { \
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(_he)[(_hn)].prev->next = (_he)[(_hn)].next; \
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} \
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if ((_he)[(_hn)].next != NULL) { \
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(_he)[(_hn)].next->prev = (_he)[(_hn)].prev; \
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} \
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(_he)[(_hn)].next = (_hs)[__hindex]; \
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(_he)[(_hn)].prev = NULL; \
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(_he)[(_hn)].pos = (_s); \
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if ((_hs)[__hindex] != NULL) { \
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(_hs)[__hindex]->prev = &((_he)[(_hn)]); \
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} \
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(_hs)[__hindex] = &((_he)[(_hn)]); \
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if (++(_hn) >= PGLZ_HISTORY_SIZE) { \
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(_hn) = 0; \
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} \
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}
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@ -454,10 +476,7 @@ pglz_find_match(PGLZ_HistEntry **hstart, char *input, char *end,
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int
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pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy)
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{
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PGLZ_HistEntry *hist_start[PGLZ_HISTORY_SIZE];
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PGLZ_HistEntry *hist_alloc;
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PGLZ_HistEntry hist_prealloc[PGLZ_HISTORY_PREALLOC];
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PGLZ_HistEntry *hist_next;
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int hist_next = 0;
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unsigned char *bp = ((unsigned char *) dest) + sizeof(PGLZ_Header);
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unsigned char *bstart = bp;
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@ -524,17 +543,12 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
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/* ----------
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* Initialize the history tables. For inputs smaller than
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* PGLZ_HISTORY_PREALLOC, we already have a big enough history
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* PGLZ_HISTORY_SIZE, we already have a big enough history
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* table on the stack frame.
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* ----------
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*/
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memset((void *) hist_start, 0, sizeof(hist_start));
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if (slen + 1 <= PGLZ_HISTORY_PREALLOC)
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hist_alloc = hist_prealloc;
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else
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hist_alloc = (PGLZ_HistEntry *)
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palloc(sizeof(PGLZ_HistEntry) * (slen + 1));
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hist_next = hist_alloc;
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memset((void *) hist_entries, 0, sizeof(hist_entries));
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/* ----------
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* Compute the maximum result size allowed by the strategy.
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@ -588,7 +602,7 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
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pglz_out_tag(ctrlp, ctrlb, ctrl, bp, match_len, match_off);
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while (match_len--)
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{
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pglz_hist_add(hist_start, hist_next, dp, dend);
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pglz_hist_add(hist_start, hist_entries, hist_next, dp, dend);
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dp++; /* Do not do this ++ in the line above! */
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/* The macro would do it four times - Jan. */
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}
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@ -600,19 +614,12 @@ pglz_compress(char *source, int slen, PGLZ_Header *dest, PGLZ_Strategy *strategy
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* ----------
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*/
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pglz_out_literal(ctrlp, ctrlb, ctrl, bp, *dp);
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pglz_hist_add(hist_start, hist_next, dp, dend);
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pglz_hist_add(hist_start, hist_entries, hist_next, dp, dend);
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dp++; /* Do not do this ++ in the line above! */
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/* The macro would do it four times - Jan. */
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}
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}
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/* ----------
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* Get rid of the history (if allocated)
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* ----------
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*/
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if (hist_alloc != hist_prealloc)
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pfree((void *) hist_alloc);
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/* ----------
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* If we are still in compressing mode, write out the last
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* control byte and determine if the compression gained the
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